1. Field of the Invention
The present invention relates to a keypad assembly provided in a portable device or a portable terminal to receive a key input from the user, and more particularly to a key pad assembly that uses a light guide panel.
2. Description of the Related Art
In recent years, it is increasingly difficult for a user to carry multiple digital application devices with various functions. Digital convergence technologies, in which various application devices are integrated into one (e.g. mobile phone), are developing. For example, various types of mobile phones combined with MP3 players, digital cameras, and game devices are presenting available.
In the digital convergence technologies, there is a need to realize respective input keys of combined devices in a mobile phone in addition to number keys and function keys essential to conduct voice communication. Since there is a large number of input symbols such as Korean letters, alphabet letters, numbers, and special symbols, but the number of realizable buttons is limited, the key limitation problem can be overcome through software but the user faces many inconveniences.
In order to solve the problem, a keypad with a display function has been suggested. In an Liquid Crystal Display (LCD) or Organic Light Emitting Diodes (OLED) display keypad, a touch screen is stacked on an LCD or an OLED and a key map is realized on the LCD or OLED through various software programs.
In other technologies, an electronic paper display keypad with an electronic paper is thin and light, and consumes little power.
However, it is difficult to apply a dome switch, used to provide a click feeling, to an LCD or OLED display keypad. Such an LCD or OLED display keypad is also thick, consumes much power, and has a poor outdoor visibility, making it difficult to identify a key map.
An electronic paper display keypad is limited in expression of colors and thus not widely selected by consumers.